Optimization Questions

The cost of a mango is 8 each, while a guava costs 6 each. A woman spends a total of 52 on these fruits. How many mangoes and guavas did she buy?

For her parents' 50th wedding anniversary celebration, Malina decides to buy $50$ balloons. Her supplier only sells balloons in bunches of $12$ for $\text{Rs. }250$ and bunches of $7$ for $\text{Rs. }175$. Malina buys exactly $50$ balloons. What is the total price she pays?

A milkman has $21\text{litres}$ of whole milk, $42\text{litres}$ of toned milk and $63\text{litres}$ of double toned milk. If he wants to pack the three types of milk in cans so that in no can two types of milk are mixed, then what is the minimum number of cans he would require?